Many catalysts have been proposed for use in the production of methacrylic acid by the gas-phase catalytic oxidation of methacrolein, isobutyraldehyde, or isobutyric acid. Most of these catalysts contain molybdenum and phosphorus as the main components and have a structure of heteropolyacid and/or salt thereof. A heteropolyacid catalyst has problems of poor moldability and low mechanical strength after molding.
Much less propositions have been made to improve the mechanical strength of a heteropolyacid catalyst than propositions to improve the performance of the catalyst, for example, the yield of methacrylic acid. Patent Document 1 proposes a molding method in which heat-resistant fiber, such as ceramic fiber, is mixed as a reinforcing agent.
Patent Document 2 proposes a molding method of a catalyst containing essential components of molybdenum and phosphorus, in which its oxide precursor and an oxide are mixed and molded.    [Patent Document 1] Japanese Patent Publication No. 2-36296    [Patent Document 2] Japanese Patent Application Laying-open No. 2004-351297